Typical photographic elements use silver halide emulsions, the silver halide having a native sensitivity to ultraviolet radiation. Ultraviolet radiation ("UV") as used in this application means light having a wavelength of 300-400 nm. Such UV sensitivity is usually undesirable in that it produces an image on the photographic element which is not visible to the human eye. Furthermore, the image dyes in the color photographs are known to fade due to action of UV light. Also other organic molecules such as unused color forming couplers in the emulsion layers and optical brighteners in the paper support degrade due to action of UV light and generate undesirable color stains on the finished photographs. Therefore, photographic elements typically contain a UV absorbing compound (sometimes referred to simply as a "UV absorber"). Another function of UV absorbers is to prevent the formation of undesirable patterns caused by electrostatic discharge in silver halide photographic materials. In general, UV absorbers impart light stability to organic molecules in various products which are susceptible to degrade as a result of the action of UV.
Generally, an effective UV absorber should have its peak absorption above a wavelength of 320 nm. The absorption peak may be at a longer wavelength, as long as absorption drops off sufficiently as it approaches the visual range (approximately 400 to 700 nm) so that no visible color is shown by the compound. In addition, to be effective, a UV absorber should have a high extinction coefficient in the desired wavelength range. However, for the most desirable UV protection, the high extinction coefficient should be at those wavelengths sufficiently below the visual range so that the compound should not be visually yellow.
UV absorbers of the benzotriazole class for photographic and other applications are well known. They include hydroxyphenyl benzotriazoles with various substituents on the hydroxyphenyl ring, including alkoxy. Compounds of the foregoing type are disclosed, for example, in Japanese published patent application JP 3139589. U.S. Pat. No. 5,112,728 discloses photographic elements with liquid hydroxyphenyl benzotriazole UV absorbers, including one example which incidentally has a racemic carbon center. Also, U.S. Pat. Nos. 4,975,360; 4,973,701 and 4,996,326 all disclose photographic elements which contain liquid hydroxyphenyl benzotriazoles as UV absorbers. U.S. Pat. Nos. 4,973,701 and 4,992,358 discuss various advantages of the absorbers being liquid. Some of the compounds in those patents include substituents on the hydroxyphenyl ring which incidentally have a racemic carbon center.
European Patent Application 0 451 813 and published Japanese Patent Application JP 04316563, disclose a photographic element containing hydroxyphenyl benzotriazoles of Formula (II): ##STR2## In formula (II) the alkyl group may be branched. A number of compounds shown in those Applications have a racemic carbon center. Another EP 0 571 935 mentioned alkoxy substituents in the phenol ring but with no specific substitution at the 4'-position in Formula (II). Moreover, the compounds of Formula (II) have been reported in the literature by M. Karvas and J. Holcik., Chemicky Prumysl, 17 (1), 543 (1967); and in Chemical Abstract 70 (12): 48169j (1969). However, as shown later, the intrinsic light stability of one of the representative compounds (III) (formula below) from those references is relatively poor. ##STR3##
UV absorbers which are currently used in photographic products include those of formula (V-A) and (V-B) below: ##STR4## However, compounds (V-A) and (V-B) have a propensity to crystallize out during cold storage of a dispersion of them.
It is therefore desirable to have other UV absorbing compounds suitable for photographic uses, which are relatively stable in a photographic environment, do not tend to crystallize out at ordinary temperatures at which photographic elements are used and/or stored, and which have a high extinction coefficient so that less of it needs to be used to obtain the same UV absorption.